Supercharger Vacuum Line Routing

[B M W Driver]

Hey All,

I've searched a lot for diagrams and threads regarding vacuum line routing but i haven't been able to find anything definitive. I just purchased a 97 m3 with a RMS Stage 2 SC with an AA tune.

I drove the car home 623 miles from Michigan with no issues besides the tune not being the best and running rich. I stayed out of boost the entire time until i was home and once i did get home i got on it a bit. I parked the car and came out a little while later to take it for a spin and that's when it developed a high idle

I noticed there was no vacuum line plugged into the bypass valve and i couldn't find anything that was loose around it. I checked the vacuum lines under the manifold and it seems like its routed incorrectly.. The current setup is as follows - The vacuum nipple under the M50 manifold closest to the firewall, has a short vacuum line going into a plastic T, one end is going under the manifold somewhere to the FPR i'm assuming. The other end is going into a check valve that goes into another plastic T. One end of that T is going into the nipple under the manifold, right behind the TB and the other end of the T is going to what looks like the Purge Valve solenoid.

On a supercharged S52, what's the correct routing path for these lines? I should also add it looks like the secondary air pump is still there but the other emissions stuff has been deleted since the car has after market headers.

Thanks in advance guys!

[B M W Driver]

Bumo

[Jamesons Viggen]

RMS might be able to help you out. I think Osh is the guy's name over there.

[pbonsalb]

The bypass valve needs a line from the intake manifold, but it can be a shared line (one with a tee). No check valve in the path to it. It is the purge valve that needs a check valve before it since you don’t want to pressurize your gas tank when in boost — you just want to suck vapor out when in vacuum. The hose you describe where one intake manifold nipple has two tees in it and then returns to another manifold nipple does not make sense, so someone who did not know what they were doing did it or was trying to cover up another issue (maybe a bypass valve with a torn internal diaphragm). Instead, one nipple could have a tee and feed the FPR and the bypass valve. The other could have a check valve and go to the purge valve. Blow through the check valve to see whicc direction blocks pressure so you orient it so pressure can it reach the purge valve.

[Braymond141]

Dinan gave the bypass valve it's own dedicated line tapped off the brake booster. Here are both shown.





Check valve for the purge valve. Comes off the nipple on #9 http://www.realoem.com/bmw/enUS/show...diagId=11_1124



Since you have no secondary air pump, there is no "correct" vacuum routing. It's really quite simple.
FPR needs vacuum
Bypass Valve needs vacuum
Tank vanting needs vacuum (and check valve orientated to keep boost from flowing out)
--- if applicable; Secondary air pump (and check valve orientated to keep boost from flowing out)

Here's an M50 manifold I added ports to (and used an aluminum manifold adapter without the nipple shown on the diagram link #9)



If you have any other valves for the oil separator drain or oil separator venting then you will need to supply those (Should only be a Dinan thing).

[B M W Driver]

Awesome, thanks for the responses everyone. I plan on going out tomorrow and rerouting the lines as you guys described. I'm assuming if reworking the lines doesn't fix my idle issue, I should then remove the aftercooler and get to the idle control valve. It's got a brand new Porsche MAF so I know it's not that.

Also just curious the line from nipple #9 that goes to the check valve and then to the purge valve, If that's T'd off after the check valve, besides the purge valve, where would the other side potentially go? Secondary air pump? If that's disconnected, anything else require vacuum? The digital boost gauge seemed to work fine and the valve cover has the plastic nipple that only has one port for the evap but no smaller vacuum port.

[B M W Driver]

So I fixed the vacuum lines today but no dice, car still has a high idle but now at start up it's 900 idling a little rough but once you give it some throttle the idle sits at 1500 2000. I took the car for a drive and it was alright, had power buy felt inconsistent.

My next guess is the idle valve though I disconnected it and it really didn't do anything. My buddy has a smoke machine I can use so I plan on doing that tomorrow

[Braymond141]

Did you drive it around to give it time to adapt? If your bypass valve was not hooked up to vacuum it was compensating.

[B M W Driver]

I took for about a 15 20 minute drive

[pbonsalb]

It seems like the PO had an issue and could not figure it out and bypassed the bypass valve, not that it was necessarily the problem. Once sorted out a forced induction car is great but a lot of owners don’t really know what they are doing and unfortunately some shops don’t either and take large quantities of your money trying to figure it out. Best to take it to someone who knows these cars even if you have to drive a long distance.

[Jamesons Viggen]

Again, you have BimmerClinic+MaxPSI not far from your house.